Femoral head arthroplasty system

A femoral head arthroplasty system comprising:

• a femoral prosthesis comprising:
• a mounting plate having a first side and an opposed second side, wherein the first side of the mounting plate is configured to abut a cut surface of the femur, and
• an implant body extending from the first side of the mounting plate, wherein the implant body extends perpendicularly from the first side of the mounting plate along a first axis by a distance no greater than 90 mm, wherein, in cross section in a plane that is perpendicular to the first axis, the implant body has a major cross sectional dimension along a second axis and a minor cross sectional dimension along a third axis that is different than the second axis, wherein the minor cross sectional dimension is less than the major cross sectional dimension, wherein the implant body is oblong in cross section in the plane that is perpendicular to the first axis, wherein the implant body has a distal end, wherein the implant body defines a continuous, uninterrupted circumferential surface extending from the mounting plate to the distal end, wherein the continuous, uninterrupted circumferential surface comprises two hemi-cylindrical surfaces having respective lengths, the two hemi-cylindrical surfaces being spaced along the second axis, and two parallel planar faces that are spaced along the third axis and extend between and to the two hemi-cylindrical surfaces along a respective entirety of each of the lengths of the two hemi-cylindrical surfaces, and wherein the implant body has a centerline that extends parallel to or is collinear with the first axis along an entire length of the implant body;
• and
• a femoral head replacement having a generally spherical surface,
• wherein one of the femoral prosthesis and the femoral head comprises an adapter, and wherein the other of the femoral prosthesis and the femoral head defines a recess that is complimentarily shaped to receive the adapter.